This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The stress hormone abscisic acid is crucial to survival of Arabidopsis upon drought stress. Key abscisic acid signal transduction proteins have YFP fusions and will be used to purify protein complexes for analyzing signal transduction partners using mass spectrometry. This research will lead to identification of new further candidate proteins that function in early abscisic acid signal transduction. The identified proteins will further be compared to guard cell specific genomic scale analyses of gene expression that have been completed using Affymetrix Genechips. Gene knockout experiments will verify the functions of the mass spectrometrically identified proteins.